The invention relates generally to methods of manufacturing magnesium diboride powders. In particular, the invention relates to methods of manufacturing doped magnesium diboride powders.
Typically, magnesium diboride is employed as a superconductor in applications such as magnetic resonance imaging (MRI), generators, motors and fault current limiters. Advantageously, magnesium diboride powders display very strongly linked current flows having large critical current densities (Jc) on the order of 107 A/cm2 in thin films. Additionally, magnesium diboride powders in the shape of wires, tapes or ribbons display Jc values on the order of 105 A/cm2. Further, the upper critical fields (Hc) and irreversibility fields (Hirr) of these powders are greater than about 30 Tesla in thin films.
Typically, magnesium diboride powders are formed by the reaction of elemental magnesium and boron. The result of this process is the production of a fine powder that exhibits high current carrying capabilities at high magnetic fields, properties that are desirable in applications, such as MRI, where large powerful magnets are required. However, the existing methods of making these powders prevent magnesium diboride from achieving the very high operating fields and critical current values, particularly, when processed into wires. This has prevented employing this technology for applications such as MRI. In consequence, these powders should be customized to enable such applications. For example, for MRI applications, it is desirable to have magnesium diboride powders, which may be drawn into thin wires without breaking while employing conventional drawing methods. In some cases, these properties may be achieved by a combination of doping and the addition of other additive materials in the composition of the magnesium diboride powders during processing of the powder. However, this doping and addition process should be carried out in such a way that prevents coating of the particles of the magnesium diboride by non-superconducting impurities. Also, it is desirable to have a uniform dispersion of the additive materials throughout the magnesium diboride powder.
Accordingly, there is a need for a method of manufacturing magnesium diboride powders and wires which have high JC and Hc values, and are configured for applications, such as MRI.